MAX17048 battery fuel gauge: specs and pinout
A breakout for the MAX17048, a single-cell lithium battery fuel gauge. It estimates state of charge from cell voltage with the ModelGauge algorithm and reports it over I2C, with an optional alert output. It does not measure current.
Specs
| Spec | Value | Source |
|---|---|---|
| Cell voltage measurement (VDD pin) | 2.5 V to 4.5 V; voltage resolution 1.25 mV/cell | source Electrical Characteristics |
| Interface | I2C, up to 400 kHz; SDA and ALRT are open-drain | source Electrical Characteristics (I2C Interface) |
| I2C slave address | Fixed 0x6C write / 0x6D read (7-bit address 0x36) | source I2C Interface, slave address |
| Supply current | Active mode 23 uA typical; hibernate mode 3 uA typical | source Electrical Characteristics |
| Input high voltage (SDA, SCL, QSTRT) | 1.4 V minimum | source Electrical Characteristics |
| Operating temperature | -40 C to +85 C | source Absolute Maximum Ratings |
| Absolute maximum, pins other than CELL | -0.3 V to +6 V | source Absolute Maximum Ratings |
| Package | 8-pin TDFN 2 mm x 2 mm, or 8-bump WLP | source General Description |
Power
| Value | Source | |
|---|---|---|
| Supply | Powered from the cell itself on VDD (2.5 V to 4.5 V); bypass VDD with 0.1 uF to GND | source Electrical Characteristics; Pin/Bump Descriptions |
| Current | 23 uA active, 3 uA hibernate (typical) | source Electrical Characteristics; Pin/Bump Descriptions |
Pinout
The pinout is the MAX17048 chip's. The breakout board's header order, pull-ups and any extra components are not covered by an official document.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| CTG (1) | Connect to ground | 0 V | TDFN pin 1 | source Pin/Bump Descriptions |
| CELL (2) | Not internally connected (MAX17048) | Voltage sense input only on the MAX17049 | source Pin/Bump Descriptions | |
| VDD (3) | Power input and battery voltage sense | 2.5 V to 4.5 V | Connect to positive battery terminal; bypass 0.1 uF to GND | source Pin/Bump Descriptions |
| GND (4) | Ground | 0 V | Connect to negative battery terminal | source Pin/Bump Descriptions |
| ALRT (5) | Open-drain active-low alert output | Optionally to a microcontroller interrupt input | source Pin/Bump Descriptions | |
| QSTRT (6) | Quick-start input | Connect to GND if not used | source Pin/Bump Descriptions | |
| SCL (7) | I2C clock input | Internal pulldown for disconnection sensing | source Pin/Bump Descriptions | |
| SDA (8) | I2C data, open-drain | Internal pulldown for disconnection sensing | source Pin/Bump Descriptions |
Build with it
Project ideas for the MAX17048 battery fuel gauge. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Battery percentage display on an ESP32: The gauge reads the single cell directly (2.5 V to 4.5 V, above the cell's 4.2 V full charge). The ESP32 board is fed 5 V from the boost board, and the protection board guards the cell. Learning project, not a safety device. SDA and ALRT are open drain (datasheet), so check the breakout has I2C pull-up resistors and add them if it does not. Pull-ups must go to the host's 3.3 V, not to the cell; check which rail the breakout's pull-ups use.
- Battery discharge curve recorder: The gauge reports state of charge over I2C and the ESP32 prints it, so you can plot how the cell falls under a known load. Learning project.
- Charge curve logger on a Raspberry Pi 5: The gauge sits on the cell terminals (VDD 2.5 V to 4.5 V, above the 4.2 V full-charge level) and the Pi reads percentage over its 3.3 V I2C bus at address 0x36. SDA and ALRT are open drain, so check the breakout has pull-ups and add them if not. Pull-ups must go to the host's 3.3 V, not to the cell; check which rail the breakout's pull-ups use. The Pi runs from its own supply. The percentage is an estimate; learning project.
Common mistakes
- Using it on a 2-cell pack: the MAX17048 senses one cell on VDD within 2.5 V to 4.5 V; the 2-cell part is the MAX17049 (source: link, Pin/Bump Descriptions)
- Expecting a current reading: the IC reports cell voltage, state of charge and rate, not current (source: link, General Description)
- Leaving QSTRT floating: the datasheet says to connect it to GND if unused (source: link, Pin/Bump Descriptions)
Not covered by the official source
- The maker's own PDF on analog.com was not used; the verbatim mirror copy of the Maxim document (Rev 7) was used.
- The sleep-mode supply current is not given here; the figure was not confirmed.
- Breakout board not covered.
Sources
- link (MAX17048/MAX17049 datasheet 19-6171 Rev 7, 11/16; maker: Maxim/Analog Devices)